Brush rigging



Dec. 31, 1946. w, GROQT 2,413,560

BRUSH RIGGING Filed NOV. 5, 1944 Inventor; Robert W. GTOOt,

His Attornes.

Patented Dec. 31, 1946 BRUSH RIGGING Robert W. Groot, Fort Wayne, Ind, assignor to General Electric Com New York pany, a corporation oi Application November 3, 1944, Serial No. 561,718

My invention relates to brush riggings and more particularly to a brush rigging adapted to be used with a dynamoelectric machine which rotates bodily.

An object of my invention is to provide an improved brush rigging.

Another object of my invention is to provide improved brush rigging for a bodily rotatable dynamoelectric machine wherein centrifugal force effects on the brush are substantially neutralized.

Further objects and advantages of my invention will become apparent from the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

.6 Claims. (Cl. 171323) In the drawing'the figure is a side elevational view of a brush rigging provided with an embodiment of my invention. 1

In certain types of dynamoelectric machines the entire machine including the stator is bodily rotatable about the axis of rotation of the rotatable member of the machine. With this type con- 1 I struction the brush rigging is subjected to centrifugal forces which may tend to vary the pressure of the brush on the current collector of the machine and produce undesirable sparking at the contact between the current collector and the brush. In my improved construction of a brush rigging adapted for this type use, the action of centrifugal force on the brush is substantially neutralized and in addition the brush holder may be constructed such that variations in the resilient biasing pressure of the biasing spring on the brush for different lengths of the brush as the brush becomes worn may also be compensated when the machine is being bodily rotated. This latter feature, however, may be omitted if desired.

As shown in the drawing the dynamoelectric machine is provided with a rotatable member mounted on a shaft l and provided with a current collector in the form of a commutator 2 adapted to be contacted by a contact brush 3. This brush *3 may be secured in any suitable manner, as by a screw 4, to the end of a brush holder biasing and supporting arm 5 which forms part of the brush rigging. As can be readily understood the brush 3 could also be arranged in a conventional box type brush holder and the biasing arm 5 could be arranged in engagement with the upper surface of the brush for biasing it towards the cur rent collector. The brush holder arm 5 is pivotally mounted by a pivot pin 6 about an axis which is substantially parallel to the axis of rotation ofthe dynamoelectric machineshaft I. In order to provide the desired pressure of the brush 3 on the commutator 2 a resilient coil spring I is arranged to exert a pressure on the brush 3 through the end of the brush holder arm 5. With this type construction centrifugal force will tend to decrease the pressure of the brush 3 on the commutator 2 when the machine including the brush rigging rotates about the axis of rotation of theshaft l, as centrifugal force will tend to throw the brush 3 and brush holder arm 5 outwardly away from the commutator surface 2. In order substantially to neutralize this action of centrifugal force on the brush pressure, I provide a second arm 5 which extends at an obtuse angle, preferably between and 160 degrees, to the brush biasing and supporting arm 5 and arranged such thatthe angle A between the second arm 8 and a radius from the axis of the machine to the center of gravity of the weight 9 is between 15 and 60 for the position of the second arm 8 for anew brush, as shown in the drawing. This arm 8 is rigidly secured to the arm 5 and may be made an integral part therewith and also may be provided, as shown in the drawing, with an added weight 9 distributed on the arm and arranged at such a length from the axis of the pivotal mounting pin 6 to provide a component decrease in moment about the axis of this pivot pin with a decrease in length of the brush 3 for substantially neutralizing the action of centrifugal force on the brush and the brush supporting arm. As shown in the figure the angle between the arms 5 and .8 is preferably approximately degrees and the position of the arm 8 for a new brush is about 45 to a radius from the center of the current collector 2 of the machine to the center of gravity of the weight 9 such that variations in the position of the arm 8 for different lengths of the brush 3 and therefore for difierent weights of the brush 3, will produce a sufficient change in the sine of the angle A between the arm 8 and the radius to the center of the machine from the weight 53 to produce a corresponding relative change in the moment arm of the arm 8 about the axis of the pivot pin it. In addition, the spring pressure of the spring '1 will decrease as the brush 7 3 becomes worn and this decrease in pressure also can be compensated for by the proper location of the center of gravity of the arm 3 and the weight 9 such that a component change in the moment of centrifugal force on this arm with a decrease in the length of the brush 3 will increase directly as the force of the biasing spring 1 decreases. This will result in maintaining a substantially constant biasing pressure of the brush 3 on the commutator 2.

The distribution of the center of gravity of the weight 9 and the arm 8, as well as the angle A between the arm 8 and the radius to the center' of the machine for a new brush can both be utilized for changing the relative moment of the arm 8 about the axis of thepivot pin 6 A change 

